This disclosure relates to a mesa shaped micro light emitting diode (LED) with the N-contact pad at the base of a mesa.
LEDs convert electrical energy into optical energy. In semiconductor LEDs, light is usually generated through recombination of electrons, originating from an n-type doped semiconductor layer, and holes originating from a p-type doped semiconductor layer. As used herein, the term “light” includes not just visible light, but also electromagnetic radiation having a wavelength outside that of the visible range, including infrared and ultraviolet radiation.
Prior bottom-emitting micro-LEDs (“μLEDs”) have a p-contact and an n-contact both formed on the top side of the μLED. In some cases, the p-contact is formed on top of a mesa structure that includes a p-type layer, a quantum well, and an n-type layer. The n-type layer extends beyond the mesa structure, and the n-contact is formed on top of this extended portion of the n-type layer. A transistor layer, such as a thin film transistor (TFT) layer, connects to the p-contact and the n-contact. The transistors apply a voltage difference between the n-contact and the p-contact which causes current to flow between the contacts and light to emit from the quantum well. The light is emitted through the bottom side of the μLED, opposite the electrical contacts and the transistor layer.
In this configuration, light emits only from the mesa structure, which is underneath the p-contact. No light emits from the area underneath the n-contact. It would be desirable to increase the amount of light extracted relative to the area of the μLED, and to increase the density of μLEDs in arrangements with multiple μLED devices. In addition, it is desirable to simplify the process of producing μLEDs to reduce cost and time of production.